Defoamer, antifoam agent or suds suppressor are terms which are used herein interchangeably to mean a material which can control a foam problem when added in low concentration to a liquid that causes foam or suds to develop during use. The defoamer equilibrates the rate of foam collapse with the rate of foam formation. Such materials, in addition, remove unsightly and troublesome surface foam, improve filtration, watering, washing, and drainage, of various types of suspensions, mixtures, and slurries. Defoamers have found application traditionally in such areas of use as the pulp and paper industry, paints and latex, coating processes, fertilizers, textiles, fermentation processes, metal working, adhesive, caulk and polymer manufacture, the sugar beet industry, oil well cement, cleaning compounds, cooling towers, and in chemical processes of varied description, such as municipal and industrial primary and secondary waste water treatment facilities. It is essential for a defoamer that it be inert and not capable of reacting with the product or system in which it is used, and that it have no adverse affect on the product or system.
The inclusion of a silicone defoamer, antifoam agent or suds suppressor in a liquid detergent is not new; however, incorporation of such a material into detergents is not without its difficulties. The reason is that it is particularly difficult to homogeneously disperse antifoam/suds suppressor formulations into aqueous media such as liquid detergents. A liquid detergent is a complex chemical formulation and often the complexity of such formulations hinders a homogeneous dispersion of an antifoam composition in the detergent. The result is often loss of uniformity, as well as flocculates of antifoam agent accumulating at the surface of the detergent.
There is also a relatively recent trend to move toward more concentrated liquid detergents. This shift offers the inherent efficiency of manufacture and use of liquid formulas, such as pumpability and easy measuring of liquids, while reducing the burden of packaging and shipping costs. This trend is occurring in both the consumer market products and in industrial formulations. The move toward concentrated liquids usually entails a reduction of the water content in a formulated liquid. This results in an increase in electrolyte and solids levels in these liquid detergent formulas. Another change is the dependence on non- aqueous solvents to aid in the solubilization of detergent components such as surfactants. Both of these changes make stabilization of antifoam droplets against physical separation and/or aggregation phenomena more difficult.
Many silicone and/or silica containing antifoam compositions have been described in the art. Such art includes, for example, Rosen, U.S. Pat. No. 4,076,648; Sinka et al., U.S. Pat. No. 4,021,365; Raleigh, U.S. Pat. No. 4,005,044; Koerner et al., U.S. Pat. No. 4,274,977; Keil, U.S. Pat. Nos. 3,784,479 and 3,984,347; Aizawa et al., U.S. Pat. Nos. 4,639,489 and 4,749,740; Starch, U.S. Pat. No. 4,983,316; John et al., EP-A-217,501; McGee et at., EP-A-341,952; Hill et al., EP-A-499,364; and Jones et al., WO 93/25652.
Notwithstanding such extensive prior art in the area of silicone-based antifoaming technology, there remains a continuing need to address the issue of the stability of the antifoam after it has been delivered to the detergent medium. The present invention centers on the discovery that, by incorporation of certain types of suds suppressor and stabilizing materials into liquid products in a certain manner, an unexpected improvement can be realized in stability against coalescence, coagulation and aggregation of the suds suppressor particles in concentrated detergent liquids. In reducing such phenomena, the present invention can improve the uniformity of dispersion of the suds suppressor agent, provide more uniform and reproducible foam control delivery and avoid the formation of unsightly lumps of aggregated antifoam droplets that may tend to sink or float in product during storage.